Bending machines that are able to right-hand and left-hand bend elongated workpieces such as pipes are already present on the market. A bending machine by BLM S.p.A., Cantù, Italy, owner of U.S. Pat. No. 6,434,993, can be cited among the others. Said patent discloses a bending machine having a bed with body and head portions, a pair of longitudinal guides on the body portion, a pair of transverse guides on the head portion, a body carriage for holding the workpiece and being mounted on the longitudinal guides, a head carriage mounted on the transverse guides, a workpiece bending assembly mounted on the head carriage and including an elongated shaft, a pair of bending dies at opposite end regions of the shaft, and a pair of bending arms each operative for bending the workpiece against a respective bending die, and a drive for turning the bending assembly about a turning axis parallel to the longitudinal axis to position a selected one of the bending dies against the workpiece to be bent, the turning drive being mounted movable along the transverse axis with the head carriage. The machine according to the above-mentioned patent, which allows, among other, any desired both right- and left-hand bending operation, is very complex.
There are also bending machines simpler than that mentioned above which allow right and left curves to be made. Examples of such machines are described in U.S. Pat. No. 2,455,138, EP-0 168 331 and U.S. Pat. No. 8,220,304. These bending machines are of the type having a fixed die and a bend arm rotating around the fixed die.
The present invention aims instead to achieve a die and counter-die type bending machine. Therein, a roller-shaped die being provided with a partial circumferential groove that is interrupted at its two ends, is driven by the shaft of a motor, and a counter-die is carried by a counter-die support member pivoted on a turret mounted on a slide which is adapted to engage the counter-die with the die. In this type of bending machine, a bending in one direction and in the opposite one can be performed by turning upside down the die and the counter-die. This operation is easy when die and counter-die are of small size, and it becomes hard and difficult if they are of large dimensions and then heavy.
A main purpose of the present invention is to provide a die and counter-die type bending machine by which an operator can change the direction of curvature, without turning upside down the die and the counter-die.
Another object of the present invention is to provide a die and counter-die type bending machine by which an operator can select and perform the curvature in one direction, and proceed with ease in the opposite direction by discharging the piece to be bent and recharging it on the same bending machine.
Still another object of the present invention is to provide a die and counter-die type bending machine by which an operator can select and perform the curvature in one direction, and proceed with ease to the curvature in the opposite direction even without discharging the piece to be bent, by virtue of a suitable choice of retaining means and the counter-die supporting turret.
These objects are achieved by a die and counter-die type bending machine in which at least one retaining means for retaining a piece to be bent is provided on the die, and a double counter-die, for right- and left-hand bending respectively is provided.
Although die and counter-die type bending machines equipped with a pair of pipe retaining means on the die already exist, they only serve to bend pipes of different diameter. See for example U.S. Pat. No. 3,921,424, U.S. Pat. No. 4,546,632 and U.S. Pat. No. 5,499,521.
U.S. Pat. No. 3,921,424 discloses a portable pipe bending comprising two matrices together in a single piece, each being equipped with a pipe retaining means. The pipe retaining means is hooks of different size provided at their end with corresponding grooves for retaining a pipe having a first diameter and a second diameter respectively. In order to change a pipe of a second diameter after having bent a pipe of a first diameter, the die needs to be turned upside down and the pipe to be attached to its retaining means. The operation for bending each pipe of different diameter occurs by clockwise rotating the die, and the discharge of the pipe is achieved by counterclockwise rotating the die. The counter-dies consist of a pair of rollers mounted on a single pivot shaft adapted to be suitably positioned depending on the diameter of the pipe to be bent.
U.S. Pat. No. 4,546,632 discloses a portable electric bender able to receive pipes of various sizes in a cone-shaped rotatable die. The die has a pair of diametrically opposite die portions, and each die portion has a plurality of curvature grooves equipped with retaining elements for retaining a pipe of different diameter. There is a similar assembly of rollers acting as a counter-die.
U.S. Pat. No. 5,499,521 discloses a bender provided with a die having a plurality of concave grooves in its outer surface. The die is provided, in a diametrically symmetrical position, with a space adapted to receive a different retaining means depending on the pipe to be retained. A pair of rollers mounted on a frame in a swinging way act as a counter-die.
Shortly, all the above mentioned three benders are intended to bend only in one direction, namely to right hand, pipes of different diameter and, in the case of U.S. Pat. No. 4,546,632, also according to curves of different radius.